The separation of aromatics from non-aromatics is a procedure of importance in the chemical and petroleum industry. Many techniques have been investigated and developed to perform the separation. Distillation under atmospheric or vacuum conditions has been employed when there is a sufficient difference in boiling point in the components to be separated. Alternatively extractive distillation or azeotropic distillation can be practiced. For mixtures of materials having little or no boiling point differentials, more sophisticated techniques must be employed, such as extraction using phenol, furfural, N-methyl pyrrolidone, sulfolane, glycols, SO.sub.2 etc. as extraction solvents, or adsorption using natural or synthetic molecular sieves (zeolites). All of these techniques are either energy intensive or require a multitude of steps (e.g. separation of the aromatics from the extraction solvents, or desorption of aromatics from the adsorbents).
Other separation techniques have been investigated. The separation of aromatics from non-aromatics by permeation through selective membranes has received significant attention in the patent literature. Various membranes have been suggested for the separation. They include various cellulose esters, cellulose ethers, mixtures of cellulose esters and ethers, polyurethanes, polyethylene, polypropylene, polyvinylidine fluoride, and polyethylene styrene copolymers.
"Separation of benzene - n Heptane Mixtures By Pervaporation with Elastomeric Membranes, (I.) Performance of Membranes" Lorchet et al., Journal of Membrane Science 15 (1983) 81-96, shows aromatic/saturate separation by pervaporation through nitrile rubber or polybutadiene acrylonitrile membranes. The nitrile membranes were lightly crosslinked with from 0.5 to 6.0% dicumyl peroxide at 160.degree.C. for 10 to 20 minutes. The article at pages 89 and 90 shows that varying the peroxide content from 0.5 to 6% did not appreciably change the performance of the membranes.